Because they officially support only ubuntu and mint. The provide a tarball for other distros but don't officially support them.

But they say "Linux" nearly everywhere, not "Ubuntu" or "Mint" (even though they're the only supported distros and the rest is best-effort tarball). There's inconsistency between iconic and textual data.

Obviously, one can't support "Linux" - that's abstract shortcut title for plethora of various GNU/Linux-based OSes. Yet, I think Tux is universally recognized symbol for those.

I have to ask: Why do you care?

This is great news, why care about the small, completely irrelevant things? Why make it look like the Linux community is blasé, whiny and will complain about anything?